The present invention relates to a fibrous binder capable of exhibiting fiber-to-fiber bonding when it is in a dry condition while the bonding ability is lost when it is converted into a hydrogel in water as well as a method for the preparation of such a fibrous binder.
As is well known, certain fibers or staples which cannot be made into paper as themselves due to the absence of self-adhesiveness or very poor self-adhesiveness thereof can be used in paper making when a water suspension thereof for paper making is admixed with a so-called fibrous binder such as fibers of polyvinyl alcohols, copolymers of ethylene and vinyl acetate, polyethylenes and polypropylenes as well as composite fibers thereof. Such a fibrous binder is used by admixing with the water suspension of the principal fibrous material for paper making and, when the sheet-like wet web of the fibers formed from the suspension is heated after drying, the fibrous binder is at least partly melted to exhibit bonding ability for the principal fibers or staples having no or little self-adhesiveness by themselves.
As a recent trend in the paper-making industry, the production is rapidly increasing of the paper products which can be rapidly disintegrated into a discrete fibrous form when put into water after use along with the increasing consumption of toilet paper and sanitary absorbent material disposable in water. The production of such water-disintegrable paper products may make a potential application of fibrous binders when the paper made by use thereof can readily be disintegrated in water.
Although various kinds of fibrous binders are known in the conventional paper-making industry as is mentioned above, none of them is suitable for use in the paper making of water-disintegrable paper products. For example, the fibrous binders made of a copolymer of ethylene and vinyl acetate, polyethylene or polypropylene are inherently very stable against and insoluble in water so that the paper made by use of such a fibrous binder can hardly be disintegrated in water into a discrete fibrous form. The fibrous binder made of a polyvinyl alcohol is also not soluble in water to be only swollen at room temperature so that the paper made by use of such a polyvinyl alcohol-made fibrous binder can be disintegrated only by a specific and troublesome treatment such as heating, addition of a chemical reagent and application of a large shearing force using, for example, a pulper machine. Accordingly, it is eagerly desired to develop a fibrous binder which can be used in making of paper rapidly disintegrable in water even under a relatively small shearing force as is given, for example, in a water flush of flush toilets.